Question

The arrow in a reaction means ? what.

Answer 1

The arrow is the process of the chemical reaction.you put the reactants before the arrow and the products after. the catalysts go above the arrow, the energy gained/loss is under (though not always). It is kind of like the equal sign (=) in math. It says that the reactants on the left side become (that's the key word) the product(s) on the right.